(1) Physical Channels and Signal Transmission on the Physical Channels in Long Term Evolution (LTE) System
FIG. 1 illustrates physical channels and a method for transmitting signals on the physical channels in a mobile communication system, 3rd Generation Project Partnership Long Term Evolution (3GPP LTE) known as Evolved Universal Terrestrial Radio Access (E-UTRA, Release 8).
Referring to FIG. 1, upon power on or when entering a new cell, a UE performs initial cell search in step S101. The initial cell search involves acquisition of synchronization to a BS. Specifically, the UE synchronizes its timing to the BS and acquires a cell Identifier (ID) and other information by receiving a Primary Synchronization CHannel (P-SCH) and a Secondary Synchronization CHannel (S-SCH) from the BS. Then the UE may acquire information broadcast in the cell by receiving a Physical Broadcast CHannel (PBCH) from the BS. During the initial cell search, the UE may monitor a downlink channel status by receiving a downlink Reference Signal (RS).
After the initial cell search, the UE may acquire detailed system information by receiving a Physical Downlink Control CHannel (PDCCH) and receiving a Physical Downlink Shared CHannel (PDSCH) based on the PDCCH in step S102.
If the UE is yet to complete its connection to the BS, the UE may perforin a random access procedure to complete the connection in step S103 to S106. During the random access procedure, the UE may transmit a predetermined sequence as a preamble on a Physical Random Access CHannel (PRACH) in step S103 and receive a response message for the random access on a PDCCH and a PDSCH associated with the PDCCH in step S104. In case of contention-based random access except for handover, the UE may perform a contention resolution procedure by transmitting an additional PRACH in step S105 and receiving a PDCCH and a PDSCH associated with the PDCCH in step S106.
After the above procedures, the UE may receive a PDCCH and/or a PDSCH from the BS in step S107 and transmit a Physical Uplink Shared CHannel (PUSCH) and/or a Physical Uplink Control CHannel (PUCCH) to the BS in step S108, which are a general downlink and uplink signal transmission procedure.
(2) Signaling of Carrier Frequency Band in LTE System
The 3GPP LTE system was designed so as to operate in the frequency bands listed in [Table 1] below. [Table 1] illustrates E-UTRA downlink and uplink frequency bands.
TABLE 1Uplink(UL)Downlink(DL)E-BS receiveBS transmitDu-UTRAUE transmitUE receiveplexBandFUL—low-FUL—highFDL—low-FDL—highMode11920 MHz-1980 MHz2110 MHz-2170 MHzFDD21850 MHz-1910 MHz1930 MHz-1990 MHzFDD31710 MHz-1785 MHz1805 MHz-1880 MHzFDD41710 MHz-1755 MHz2110 MHz-2155 MHzFDD5824 MHz-849 MHz869 MHz-894 MHzFDD6830 MHz-840 MHz875 MHz-885 MHzFDD72500 MHz-2570 MHz2620 MHz-2690 MHzFDD8880 MHz-915 MHz925 MHz-960 MHzFDD91749.9 MHz-1784.9 MHz1844.9 MHz-1879.9 MHzFDD101710 MHz-1770 MHz2110 MHz-2170 MHzFDD111427.9 MHz-1452.9 MHz1475.9 MHz-1500.9 MHzFDD12698 MHz-716 MHz728 MHz-746 MHzFDD13777 MHz-787 MHz746 MHz-756 MHzFDD14788 MHz-798 MHz758 MHz-768 MHzFDD. . .17704 MHz-716 MHz734 MHz-746 MHzFDD. . .331900 MHz-1920 MHz1900 MHz-1920 MHzTDD342010 MHz-2025 MHz2010 MHz-2025 MHzTDD351850 MHz-1910 MHz1850 MHz-1910 MHzTDD361930 MHz-1990 MHz1930 MHz-1990 MHzTDD371910 MHz-1930 MHz1910 MHz-1930 MHzTDD382570 MHz-2620 MHz2570 MHz-2620 MHzTDD391880 MHz-1920 MHz1880 MHz-1920 MHzTDD402300 MHz-2400 MHz2300 MHz-2400 MHzTDD
As noted from [Table 1], when the 3GPP LTE system operates in Frequency Division Duplex (FDD), different downlink and uplink frequency bands are mapped to each other, whereas when the 3GPP LTE system operates in Time Division Duplex (TDD), one frequency band is divided in time for downlink and uplink transmissions. A cell uses a single frequency band in TDD and a pair of frequency bands in FDD. A BS may manage a plurality of cells that are distinguished spatially or by different frequency bands. In [Table 1], the channel raster is 100 KHz, which defines a central frequency that the UE should scan for initial synchronization to the BS. This means that the central frequency of each carrier frequency should be a multiple of 100 KHz. Downlink and uplink carrier frequencies and their bandwidths are signaled as system information in the form of E-UTRA Absolute Radio Frequency Channel Numbers (EARFCNs). In FDD, different downlink and uplink frequency bands are paired and the EARFCN of the uplink frequency band is transmitted to the UE. For handover in an environment where there are a plurality of neighbor cells distinguished by different frequency bands, the EARFCNs of the frequency bands of the cells are broadcast as system information, for handover to the cells.
[Table 2] lists the channel numbers of E-UTRA frequency bands.
TABLE 2E-UTRADownlinkUplinkBandFDL_low [MHz]NOffs-DLRange of NDLFUL_low [MHz]NOffs-ULRange of NUL121100 0-59919201300013000-1359921930600 600-119918501360013600-141993180512001200-194917101420014200-149494211019501950-239917101495014950-15399586924002400-26498241540015400-15649687526502650-27498301565015650-157497262027502750-344925001575015750-16449892534503450-37998801645016450-1679991844.938003800-41491749.91680016800-1714910211041504150-474917101715017150-17749111475.947504750-49991427.91775017750-179991272850005000-51796981800018000-181791374651805180-52797771818018180-182791475852805280-53797881828018280-18379. . .3319002600026000-2619919002600026000-261993420102620026200-2634920102620026200-263493518502635026350-2694918502635026350-269493619302695026950-2754919302695026950-275493719102755027550-2774919102755027550-277493825702775027750-2824925702775027750-282493918802825028250-2864918802825028250-286494023002865028650-2964923002865028650-29649
Referring to [Table 2], a downlink EARFCN and a downlink carrier frequency in MHz satisfy the following equation.FDL=FDL—low+0.1(NDL−NOffs-DL)  [Equation 1]where FDL represents the highest frequency of a downlink frequency band, FDL—low represents the lowest frequency of the downlink frequency band, Noffs-DL represents an offset, and NDL represents the downlink EARFCN.
In [Table 2], an uplink EARFCN and an uplink carrier frequency in MHz satisfy the following equation.FULFUL—low+0.1(NUL−NOffs-UL)  [Equation 2]where FUL represents the highest frequency of an uplink frequency band, FUL—low represents the lowest frequency of the uplink frequency band, Noffs-UL represents an offset, and NUL represents the uplink EARFCN.
FIG. 2 illustrates an LTE system using a single component carrier. Referring to FIG. 2, transmission and reception each are performed in one frequency band in the LTE system. If transmission and reception are intended in neighbor frequency bands, inter-frequency handover is performed to thereby change the carrier frequency.
FIG. 3 illustrates a multi-carrier system. In the multi-carrier system, a UE may receive a plurality of component carriers simultaneously. When component carriers are contiguous as illustrated in FIG. 3, the entire component carriers may be subjected to Fast Fourier Transform (FFT) and then the FFT signal may be amplified by a power amplifier, for Orthogonal Frequency Division Multiplexing (OFDM) transmission. If the same pattern of downlink Reference Signals (RSs) is used for every component carrier, a CM value that affects the backoff of the power amplifier increases.
[Table 3] below lists CM measurements when downlink RSs are transmitted in the same pattern in every component carrier.
TABLE 3w/o PSFCMQPSKOFDM#F-Block12345RS only1Tx4.026.578.5910.1311.32Rank1ANT14.026.528.5810.1311.32ANT23.986.568.5910.1111.342Tx ANT13.986.528.5910.1511.35Rank2ANT23.986.528.6110.1311.35RS(0 dB) +1Tx4.024.124.274.424.58dataRank1ANT13.994.174.374.604.82ANT23.994.174.374.594.822Tx ANT14.004.174.384.584.81Rank2ANT24.014.164.374.574.82RS(3 dB1Tx4.004.324.735.125.52boost) + Rank1ANT14.004.434.945.455.95dataANT24.004.444.965.445.952TxANT14.004.434.935.445.95Rank2ANT24.004.444.955.465.95RS(6 dB1Tx4.004.725.546.286.97boost) +Rank1ANT14.004.895.866.717.50dataANT23.994.885.846.727.512Tx ANT14.024.885.846.717.50Rank2ANT24.014.885.856.737.48RS(9 dB1Tx4.015.256.527.588.50boost) + Rank1ANT14.005.426.797.958.92dataANT24.005.416.817.968.932Tx ANT14.025.416.797.988.91Rank2ANT23.995.436.797.958.93
Referring to [Table 3], it is revealed that while in case of transmitting an RS and data at the same power ratio, an increase of component carriers in number leads to a negligibly small CM increase, the CM increases significantly due to the increase of component carriers in number, when RS power is boosted. Accordingly, there exists a need for minimizing a CM increase in a multi-carrier system.